import pandas as pd
s5 = pd.Series([10, 20, None, 30])
print(s5.isnull())     # 检测缺失值
print(s5.fillna(0))    # 用0填充缺失值
print(s5.dropna())     # 删除缺失值
print(s5.astype('float'))  # 转换为浮点型
